1. Field of the Invention
The present invention relates to solar heat collectors and their combination with conventional heat pumps and, in particular, to a new and useful passive solar assistance device for use with a conventional heat pump to provide a source of heat for the heat pump in winter months or a heat sink for the heat pump when it is operated as a cooling unit in summer months.
2. Description of the Prior Art
Various solar heat collecting devices are known for utilizing the heat radiated from the sun. Solar heat collectors are also known which incorporate heat pipes for transporting this heat. Examples of these devices are found in U.S. Pat. No. 4,119,985 to Knowles et al. and U.S. Pat. No. 3,996,919 to Hepp.
Heat pumps are known which are driven by electricity and operated to pump heat to areas of relatively low temperature from areas of higher temperature. These conventional heat pumps may be operated either as cooling or refrigeration units for removing unwanted heat from one location and discharging it into another, or conversely, as heaters for removing heat from one location and discharging it into another area which requires heat. An electrically driven heat pump operates on the same principles as vapor-compressing space cooling units or air conditioners. Unlike a conventional air conditioner however, a heat pump has the additional capacity of providing winter space heating for buildings by, in effect, cooling the exterior ambient air and discharging the heat gained by this cooling to the interior of the building. Heat is drawn from the outside ambient air even when the temperature of this air falls below 70.degree. F. An electrically driven heat pump is capable of providing two to four times the heat which can be provided by an electric resistance heater which uses an equivalent amount of electrical energy. This ratio of heat delivered by a heat pump to the amount of heat delivered by an electric resistance heater where both systems use an equivalent amount of electricity, is called the coefficient of performance or COP. The COP of heat pumps are generally in the range of about 2 to about 4.
The effectiveness of heat pumps however, is limited by the fact that they will operate and provide a COP of 2 to 4 only when the outdoor air temperature is greater than between about 45.degree. to 50.degree. F. At lower temperatures, the COP is reduced until, at a temperature of about 10.degree. to 20.degree. F., the heat pump can no longer of effectively draw any heat from the ambient outside air. At temperatures lower than these therefore, use must be made of electric resistance heating which has a COP of 1.
When a heat pump is used in its cooling mode, that is to act as an air conditioner for cooling a building, its efficiency and usefullness again will depend on the outside temperature and the heat pump's ability to shed excess heat drawn from the interior of the building. In a heating mode therefore, the effectiveness of a heat pump will depend on the heat which can be provided thereto and, in its cooling mode, the effectiveness of the heat pump will depend on its ability to shed excess heat.